1. Field of the Invention
The present invention relates to an apparatus for supporting docking of a marine vessel, and to a marine vessel including the apparatus. The term “docking” as used herein means that the marine vessel is brought into contact with a docking site (e.g., a pier, a wharf, a second marine vessel, or the like) or into close proximity to the docking site.
2. Description of the Related Art
A prior art technique for supporting a marine vessel maneuvering operation for docking a marine vessel is disclosed in Japanese Unexamined Patent Publication No. 2005-28891. According to the prior art technique, a pair of bitts (an object to be approached for docking) are provided on a wharf, and the marine vessel includes two pairs of automatic object tracking laser distance measuring apparatuses which each include a TV camera having an automatic tracking function and a laser distance sensor. The automatic object tracking laser distance measuring apparatus automatically tracks the bitts on the wharf, and constantly measures distances to the respective bitts. Based on the results of the measurement, the position of the marine vessel with respect to the wharf and the attitude and approaching speed of the marine vessel are computed, and the results of the computation are displayed on a display device. With reference to the display, an operator of the marine vessel controls bow side thrusters and stern pod propellers.
The prior art technique disclosed in Japanese Unexamined Patent Publication No. 2005-28891 is based on the assumption that the bitts are preliminarily provided on the wharf, and principally intended to support the docking of a large-scale marine vessel such as a large-scale ferry or a large-scale tanker. In the case of the large-scale marine vessel, a docking site (a site of a pier at which the marine vessel is to be docked) is predetermined according to a navigation schedule. Of course, the docking site is preliminarily selected so as to ensure safe docking of the large-scale marine vessel.
On the other hand, a small-scale marine vessel such as a cruiser, a fishing boat, a water jet, or a watercraft can berth in a narrow space in a harbor, so that it is rare to preliminarily assign a docking site to the small-scale marine vessel. Therefore, an operator of the small-scale marine vessel finds an available docking site in the harbor and, after visually checking the docking site for safety, docks the marine vessel at the site.
For example, the marine vessel may be re-docked at a docking site which is defined as a target docking position when the marine vessel leaves the docking site. However, if another marine vessel berths at that docking site, the target docking position should be changed. Of course, it is impossible to preliminarily determine a docking site in a harbor to be visited for the first time by the marine vessel. Further, a change in water depth due to tides may prevent the re-docking of the marine vessel at the docking site from which the marine vessel sets off.
For these reasons, the prior art technique disclosed in Japanese Unexamined Patent Publication No. 2005-28891 is not applicable to the support of the docking of the small-scale marine vessel. Therefore, whether or not the small-scale marine vessel can be safely docked at a docking site depends heavily on a judgment made by the operator of the marine vessel. Particularly, most leisure boat operators have insufficient marine vessel maneuvering skill and, therefore, often fail to make a proper judgment on the safe docking site.